A fuel cell system employing a polymer electrolyte membrane fuel cell (PEMFC) includes a fuel cell main body that is referred to as a stack, a reformer that reforms the fuel to generate a reforming gas containing hydrogen and that supplies the reforming gas to the fuel cell main body, and an oxidant gas supply unit that supplies an oxidant gas to the oxidant gas supply unit. The oxidant gas supply unit generates electrical energy through an electrochemical reaction of the reforming gas, supplied from the reformer, and the oxidant gas, supplied from the oxidant gas supply unit.
In such a fuel cell system employing the polymer electrolyte membrane fuel cell, a conventional reformer includes a thermal source unit that generates thermal energy, a reforming reaction unit that generates the reforming gas containing hydrogen through a reforming reaction of the fuel using the thermal energy, and a carbon monoxide reduction unit that reduces a concentration of carbon monoxide contained in the reforming gas.
In the conventional reformer, thermal energy corresponding to unique operational temperature ranges of the reforming reaction unit and the carbon monoxide reduction unit are supplied to the reforming reaction unit and the carbon monoxide reduction unit at the time of initial driving of the reformer in order to obtain optimal operational efficiency. However, it is difficult to control the thermal energy supplied from the thermal source unit to the reforming reaction unit and the carbon monoxide reduction unit. Therefore, the operational efficiency of the reformer is limited.